Hi to all. I am new to Black Powder Cartridge Rifle shooting and loading. I have cast and loaded for handguns in the past. I was recently introduced to "Ram Bash" shooting here in Virginia and was immediately hooked. I was fortunate enough to be able to purchase a Shiloh Montana Rough Rider used. I am told that it is 1994 production and was originally a 45-70, but was re-barreled as a 40-65 by John King some twenty years ago. I am also told that the gun went for many years without being fired. I'm told that it has a Badger Barrel and if I measured it correctly has a 1:18 twist. The rifle actually came with a set of RCBS Cowboy dies and a Lyman 2640678 mold as well as a couple hundred cartridge cases.
I made a camber casting as well as slugged the bore. What I am learning is that my bullets drop at 392 grains in pure lead with a dab of tin. I have an old Starret micrometer that only shows down to .001. The bullets that I have measured are out of round and vary from .408 to .409+ as they are rotated in the micrometer. If I slugged and measured correctly I am getting .409+ as a groove diameter in my rifle (at the muzzle) My chamber casting shows that the bullet needs to make a pretty good jump before engaging the riffling.
I'm bewildered about what mold to select going forward and wondering if I would be better served by a custom mold. I would like to send my chamber casting and slug to someone who can supply me with a good mold for my purposes. I will be loading mostly Black Powder, but probably some smokeless as well.
Here is a target shot at 100 yards off of a rest of ten shots, starting with a clean barrel:
I don't know if the image works or not. That load is 58 grains of Swiss 1 1/2 with a .030 vegetable wad. Winchester Large Rifle primer.

1-25 or 1-30 alloy should be fine.
Pan or Dip Lubing the bullets should work just fine.
Seat the bullet out to just touch the rifling with at least some powder, adding wad stack may be necessary, compression and go to Ram Bash.

What DD said. Get the bullet out to touch the lands, load by volume with either a veggie or poly wad (0.060" compression works well for me with Swiss 1.5Fg in most rifles, but YYMV).

Check your mould by holding it up to the light with the sprue plate turned open. If you can see light between the halves, the mould is not closing properly and that is the reason for the out-of-round. If closing properly, I'd not worry about it too much-it will conform to the barrel when the fire is lit.

Good luck with learning to load for these rifles! It's been a lifelong pursuit for many of us.

Thanx for the responses. I may be splitting hairs and don't need to worry. Since these bullets are soft and get bumped up anyway perhaps I don't need to fret. I'm going to keep shooting what I've got for a while.

I would not worry about .001" out of round. Like you said they will bump up to fit the barrel anyway. The Saeco 740 is a good production bullet for the 40 caliber rifles. When you are ready for a custom mold take a look at the ones offered by Buffalo Arms. They offer quite a variety of styles in 40 caliber.

"Perfection consists not so much in doing extraordinary things as in doing ordinary things extraordinarily well"